Diagnostic information monitoring system



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DIAGNOSTIC INFORMATION MONITORING SYSTEM Filed April 2v, 1949 1o sheets-sheet 1 0 03 0 R @o2 9 a 4 808 e 6/5 ao/ s/sA/AL Pl/L sf P our /M/Wrol? R/cHA/w ft @may Patented Apr. 7, 1953 DIAGNOSTIC INFORMATION MONITORING SYSTEM Richard M. Bloch, Waltham, Mass., assignor to Raytheon Manufacturing Company, Newton, Mass., a corporation of Delaware Application April 27, 1949, Serial No. 89,871 y 41 Claims.

This invention relates in general to the handling of information in the form of time-varied electric waves, and more particularly to methods of and means for supervising the accuracy of and correct handling of such information.

It is known to supervise or monitor the identity of an electric wave which is being transferred from one place to another by means of another electric wave identical with the first and transferred therewith or subsequently thereto. Such a procedure requires either complete duplicate handling equipment or a complete repetition of the operation being supervised. Likewise, it is known, in the art of electronic and electrical computing machines, to supervise the operations of such machines by sending the same problem through twice simultaneously or twice in succession. The former process again requires complete duplicate equipment, and the latter process obviously consumes double the time required merely to perform the desired operations.

The present invention provides means to monitor information in the form of time-varied electric waves which creates for each item of information a characteristic time-varied electric wave of a prescribed short duration which is employed as an indicator and is thereafter carried 'with the main electric wave as an additional, readily separable part thereof. Each time the main electric wave is handled, the indicator is Icreated anew, and the new indicator is then compared with the indicator that is carried with the main electric wave for the purpose of ascertain- 'ing whether or not the main electric wave has undergone any change. The amount of additional equipment required to provide the indicators is approximately twenty per cent as extensive as the equipment that handles the main information, while the simultaneity of systems employing complete duplicate equipment is substantially preserved. Further, the present system 4is diagnostic for the reason that a new indicator is created from the main wave each time it is handled or transferred, so that the place in a complete system where a fault may have occurred can be readily known. The present invention is adaptable to use with limitless forms of information handling systems and various kinds of wave forms. It has utility, for example, in telemetering systems of all kinds and varieties, and in electrical computing machines of all degrees of complexity.

In its use in computing machines, the invention is particularly valuable in that it may be modified in many Ways to supervise :not only the idQIl-tity of information which is transferred from place to place within the machine, but also the accuracy of mathematical operations performed upon such information. Thus, for example, an addition of two quantities which are represented by first and second electric waves is supervised by means which creates from each wave a short indicator wave in accordance with a prescribed scheme, then creates from the sum of the two original waves a third short indicator wave, and then operates upon these indicator waves in a prescribed manner to produce an electric wave which has only one possible form if the addition was performed correctly. The means for accomplishing this supervision is again small in extent as compared with the main computing equipment, and functions practically simultaneously therewith. Other processes of subtraction, multiplication, and division are supervised by analogous means and methods.

While the invention is not limited in its employment to any particular form of electric wave, it is most easily understood in connection with systems which store and transfer information in the form of electric waves consisting of groups of discrete pulses. Digital telemetering systems and computing machines employing the binary system of notation employ such groups of discrete pulses to represent information items. In one form, a group of discrete pulses represents a binary number by providing a pulse space in a train of time-spaced spaces for each digit of the number, the presence of an electric pulse in a space representing a 1 and the absence of a vpulse in a space representing a 0.

When the information which is being handled in the binary notation system originates in the decimal system, it must be converted to the binary form. Similarly, end-product information is often converted to the decimal form. The present invention employs means which supervises the accuracy of such conversions, also, by creating indicators for the quantity being converted, the conversion product, and the unconverted remainder, the indicators being Vcreated in accordance with a scheme such that their sum results at all times in an electric wave which can have only one possible form if the conversion has been effected correctly.

The foregoing and other features of the invention will become more apparent from the detailed description of certain specific embodiments that follows. The description refers to the accompanying drawings, wherein:

Fig. 1 is a, block diagram of a system which generates a four-column binary indicator from any multi-columnar series of pulses and pulse spaces representing, for example, a binary number;

Fig. 2 is a circuit diagram illustrating certain details of Fig. 1;

Fig. 3 is a block diagram illustrating one phase of the operation of Fig. 1;

Fig. 4 is a block diagram illustrating another phase of the operation of Fig. 1;

Fig. 5 is a diagram showing a group of timespaced pulses representing an item of information in binary notation as handled in accordance with the invention;

Fig. 6 is a block diagram of a system which supervises the identity of a group of pulses like that shown in Fig. 5 which is being transferred from one location to another;

Fig. 'l is a circuit diagram of an arrangement which may be employed for sensing or coincidence checking in the systems shown vin Fig. 6 and Fig. 8;

Fig. S is a block diagram of a system which supervises the correct performance of an arithmetic operation upon two binary quantities;

Figs. 8A, 8B and 8C are modiiications of the system of Fig. 8;

Fig. 9 is a block diagram of a suitable weighting circuit for use in the system of Fig. 8;

Fig. 10 is a block diagram of a system which supervises the accuracy of conversions between the binary and decimal systems of notation;

Fig. 11 is a chronological diagram illustrating the time relationship existing among certain of Monitoring the identity of information Referring now to Fig. l, a binary number consisting of a chronological series of Voltage pulses Il, for which an indicator is to be generated, is provided from a binary number input source represented by a bloei: It. The pulses I'I may be either positive or negative, as desired. In the present description, negative pulses are illustrated. The pulses Il' of the number from the block it are sequentially provided in parallel to three gates il, i2 and It, which may be called weighting gates #1, #2 and #3, respectively. The three weighting gates are normally closed, in the sense that they do not permit the pulse Il to pass, and are operated to an open, or pulsepassing, condition by means of negative gate control pulses !3 furnished by a pulse generator 4I via two delay lines i5 and I5. The binary number consists of a chronological series of pulse spaces, each of which may or may not be occupied by a pulse Il, which spaces are repeated at a predetermined repetition frequency. The pulse generator It furnishes gate control pulses i8 at a pulse repetition frequency which is onethird that oi the binary number. A synchronizing pulse i3, furnished from a suitable master timing source (not shown), is furnished to both the binary number input lli and the' pulse generator I t in order that each gate control pulse I 8 shall occur simultaneously with a predetercri mined number pulse I I or pulse space of the binary number. The gate control pulse I il is applied directly to weighting gate #1, and at the same time to the rst delay line l5. The pulse which emerges from the first delay line I5 is applied directly to weighting gate #2 and at the same time to the second delay line IE. The pulse which emerges from the second delay line it is applied directly to weighting gate #3. The gate control puise i3 is delayed in each delay line I5 and iii by an amount equal to the spacing between two adjacent pulses Il of the binary number which occupy adjacent iulse spaces. The effect oi this arrangement is that pulses Il' which cccupy successive pulse spaces of the binary number from the-input Iii pass through successive gates from gate #1 to gate #3 and then back to gate #1.

Four nip-flop circuits, of a kind to be clescribed below, are represented by blocks 2i, 22, 23 and 25, respectively. These blocks are in columns i, 5, and Il, respectively, ci a binary system binary number pulse Il which passes 'hrough weighting gate #l is provided to the column I nip-flop 2l via a signal input line 2S, the number pulse il passing through gate #2 to the coiumn 2 nip-flop 22 via a signal input line El, and the number pulse passing through gate #3 to the column 3 flip-flop 23 via a signal input line 2t. The column t nip-flop 24 is provided with a signal input line 29. .as will be explfined below, each of the flip-flops El to 24, in-

lusive, arranged so that it will change state each i'lce a number pulse il is applied via its signal input line 25, 2i, 28 or 29, respectively. Each of the nip-ops 2| to 24, inclusive, is provided also with a signal output line 3l, 32, 33 and 34, respectively, in which negative output voltage pulses 92 appear. An amplifier A may be included in each output line, if desired. In each nip-flop, one state-of the flip-flop represents the digit 1 standing in the column of the nip-flop, while the other state represents the digit 0 standing in the column. When the nip-flop changes from the l state to the 0 state, a pulse appears in its output line, as will be explained more in detail below.

The output line 3l of the column I iip-rlop 2l is connected by way of a rst carry gate 3S to the signal input line 21 of the column 2 nip-flop 22. The output line 32 of the column 2 flip-nop is connected by Way of a second carry gate 3l to the signal input line 28 of the column 3 flip-nop 23. The output line 33 of the column 3 flip-nop is connected by way of a third carry gate 33 to the signal input line 29 of the column t nip-nop 24. The carry gates 35, 31 and 38 are all normally closed in the sense that they do not permit the output pulse S2 to pass, and are simultaneously operated to an open or pulse-passing condition by a negative pulse 4D furnished by a count control pulse generator 39 which is connected to all three carry gates in parallel. The pulse 15D furnished by the countl control pulse generator 39 occurs simultaneously with each binary number pulse or pulse space, the generator 39 being controlled, if desired, by the same central synchronising mechanism (not shown) which provides the synchronizing pulse I9.

The four nip-flops 2l to 24, inclusive, and their associated carry gates 36 tov 38, inclusive, may be termed a register here a four-column register. The simultaneous states of the individual iip-ops at any one instant define a four-column binary quantity, which quantity is said to stand in the register at that instant. The

rentby a suitable capacitor 59.

quantity which stands in the register at the end of the operation upon the binary number for which an indicator is created is the indicator. The manner in which the register is operated to create an indicator will be presently explained in greater detail in connection with Fig. 3.

The signal output line 34 of the column 4 flipop 24 is connected by way of a shift gate 46 and a delay line 44 to a first side input line 4| of the column 3 flip-flop 23. The signal output line 33 of the column 3 flip-flop is connected by Way of a shift gate 41 and a delay line 43 to a first side input line 35 of the column 2 flip-flop 22. The signal output line 32 of the column 2 flip-flop is connected by way of a shift gate 48 and a delay line 42 to a first side input line 30 of the column I flip-flop 2|. The signal output line 3| of the column I flip-fiop is connected by way of a shift gate 49 to a serial read-out terminal 50. The shift gates 46, 41, 48 and 49 are all normally closed in the sense that they do not permit the output pulse 92 to pass, and are simultaneously operated to an open, or pulse-passing, condition by a negative pulse 93, furnished by a shift read-out control pulse generator 5| which is connected to all the shift gates in parallel. The shift read-out control pulse generator 5| is operated only when it is desired to remove or read out the information standing in the register, namely, the indicator of the main binary number. A reset pulse generator .i

which produces negative reset pulses 86 is connected in parallel to a second side input line 45 of each of the flip-flops 2| to 24, inclusive. The reset pulse generator is operated in cooperation with the shift read-out control pulse generator 5| during a read-out operation, as will presently be explained in connection with Fig. 4. The delay lines 42, 43 and 44 provide a time delay to the passage of the output pulses 92 furnished thereto which is substantially longer than the duration of a shift read-out pulse 93.

A single-pulse generator which produces a single negative pulse 95 at the end of the indicator-creating operation, is connected to the signal input line 26 of the column flip-iiop 2| for the purpose of adding the binary quantity l to whatever binary quantity stands in the register at the end of the operation wherein an indicator is created, and prior to reading out the indicator.

The purpose of adding 1 will also be presently exi plained.

Referring now to Fig. 2, the circuits therein illlustrated are the column and column 2 flipflops 2| and 22, respectively. Considering the column flip-flop 2|, the circuit is basically an .f

Eccles-Jordan circuit including first and second triodes 54 and 55, respectively, connected at their anodes to an anode voltage terminal B+, via anode resistors 56 and 51, respectively, and at their cathodes to a common ground via a. cathode resistor 58, which is bypassed for alternating cur- An inductor 60 is connected between the anode resistor 51 of the second triode and the B+ terminal. A diode 84 is connected in shunt with the inductor, the cathode being connected to the B+ end thereof. Each anode of each triode is connected via a suitable parallel-resistance-capacitance circuit 6| or 62 to the control grid 64 or 1| of the other triode. The control grid 1| of triode 55 is connected to the output line 32 of the column 2 flip-flop 22 via the delay line 42, the shift gate 48, the first side input line 30, a capacitor 12, and a diode 13 in series, the anode of the diode 13 being connected to the grid 1|, A resistor 15 is connected between the fil) grid 1| and ground. A resistor 14 is yconnected between the cathode of the diode 13 and theA cath'- ode of the triode 55. By this connection to the grid of triode 55, an output pulse 92 from the column 2 iiip-iiop 22 is impressed upon the column flip-flop 2| if the shift gate 48 is in an open condition. The reset pulse generator 20 is connected to the control grid 64 of triode 54 by way of the second side input line 45, a, capacitor 81, and a diode 65 in series, the anode lof diode 65 being connected to the grid 64 and the cathode of diode 65 being connected to the cathode of the triode 54 via a resistor 61. A resistor 66 is connected between the control grid 64 and ground.

Thus far, the circuit of the two triodes 54 and will be recognized as the well-known Eccles- Jordan circuit which can be triggered at either of the control grids 64 or 1| by means of a negative pulse applied at the cathode of the diode or 13, respectively. Each of the control grids 64 and 1| has a second diode 11 and 1B, respectively, connected thereto at its anode. The cathodes of these second diodes are connected together and via a coupling capacitor 19 to the signal input line 26 which is connected to Weighting gate #1. A resistor is connected from the cathodes of the second diodes 11 and 1B to the cathodes of the triodes 54 and 55. A negative pulse l1 brought into the flip-nop via the input line 26 will change the state of the flip-flop regardless of its preexisting state. A negative pulse 86 or 92, which is brought into the nip-flop at one side or the other only, will change the state of the flip-flop only if the triode to which it is applied is previously in a conductive state.

The output signal line 3| of the iiip-iiop is connected via a coupling capacitor 83 to the junction point 52 of the anode circuit resistor 51 of the second triode 55 and the inductor 60. The diode 84 is connected at its anode to said junction point. When the second triode 55 is rendered non-conductive, the potential of the anode thereof assumes a high state, and, when this triode is rendered conductive, the anode potential thereof assumes a low state. The Eccles-Jordan circuit of the flip-flop is so dimensioned that it can occupy only one state wherein the first triode 54 is conductive and the second triode 55 is nonconductive, or the opposite state, and its state is abruptly changed by a negative pulse such as the pulse |1, 86 or 92 properly applied thereto. When the second triode 55 is abruptly rendered conductive, current begins abruptly to flow through the inductor 60. During the initial surge of current, the junction point 52 of the inductor and the anode resistor 51 undergoes a correspondingly abrupt change in potential in the negative direction with respect to the B+ terminal, and thereafter a substantially exponential change in potential in the positive direction, returning eventually substantially to the potential level of the B+ terminal. These changes produce the output pulse 92. Any tendency of the junction point 52 to assume a potential which is positive with relation to the B+ terminal is inhibited by the diode 84 which is shunted across the inductor 60, since the diode becomes conductive when that happens and shortcircuits the inductor. Thus, when the second triode 55 is abruptly rendered noncondu-ctive, no positive pulse corresponding to the negative pulse 92 is produced. The diode 84 is thus employed as a dioderclamp, and it will be recognized by those skilled in the art that a crystal or other form of dry rectifier may be employed in place of an electron-tube diode, if desired.

.15a-,secolari The circuit of -the column 2 dip-nop 22 is identical to that of the column l flip-nop El and will not be described in detail. Similar elements of both circuits bear the same reference characters. Likewise, the column 3 and i flip-ops 23 and 24, which are not shown in Fig. 2, have similar circuits to that of the column l. rhe column `i flip-flop 24, however, has no input line to the first side thereof, and accordingly, in column d, the rst side input diode l, and its resistor hl and capacitor l2, may be omitted, if desired.

Each nip-flop is operated by negative pulses. The input pulse ll from a Weighting gate is a negative pulse applied to the cathodes of input diodes 'il and 'IS in parallel. This pulse cuts ofi the triode 54 or 55 which is conductive, thereby rendering-the other triode conductive. The output pulse 92 from a shift gate 46, il? or 6.8 is negative, and is applied through the capacitor 'I2 and first side input diode I3 to the control grid 'H of the second triode 55, and is effective to cut off triode 55 should that tube be conducting when pulse 92 arrives. The reset pulse S5 from the reset pulse generator 2i! is negative, and is applied through a capacitor d? and second side input diode -'e' to the control grid t4 of the nrst triode 54, and is effective to cut oi triode 54 in the event that the tube is conducting when the reset pulse 85 arrives. Thus, the pulse Il from the Weighting gate causes a change of state of the flip-flop regardless of the state thereof at the time pulse il arrives, While the reset pulse 238 or the output pulse $32 changes the state of the nip-flop only if the triode to which it is applied is conductive at the time of application.

It is important to remember that the output of each nip-flop 2i to 24, inclusive, is either a negative pulse E32 or no pulse at all. As a matter of definition, it may be stated that, when the second triode 55 is in a nonconductive condition, a "1 stands in the flip-flop, and, when triode 55 is in a conductive condition, a 9 stands in the flip-flop. The basis of this deiinition is that the negative pulse 92, Which the flip-ncp will furnish When the second triode 55 is rendered conductive, is employed to represent the digit i being extracted from the nip-flop. In accordance with this denition, When the negative reset pulse 86 is furnish-ed to the flip-flops, it

causes all four nip-flops to stand simultaneously at zero.

The various gates of the system of Fig. i may be constructed in accordance With Fig. 13, if desired. In Fig. 13, a signal input pulse dill is applied at a signal input terminal 8d2. Terminal (5@2 is connected to one side of an input coupling capacitor 8c3, which is connected at the other side to the junction 804 of a resistor S95 and -a unidirectional conductor 8&5. The unidirectional conductor 8535 and others shown and described herein may be of any desired form, for example, an electron tube diode or a crystal or other form of rectifier may be used, and will hereafter be referred to simply as a rectier. The function of rectier Scsi is essentially that of a clamp, and it is poled to conduct current to ground at sill whenever the junction 8134 becomes positive with respect to ground. In this manner, the signal pulse is maintained practically purely negative.

Resistor B is connected at its other end to the junction S of a second rectifier Stil and one side of an output coupling capacitor Eli.

The second rectifier 399 is connected to ground at 852 via a second resistor 813, and is poled to become conductive between ground and junoltion B08' Whenever-the junction 868 is negative -With respect to the grounded side of the rectier. The junction Bld of this grounded side and the second resistor 813 is connected via a gate pulse coupling capacitor S15 to a terminal Sie via which a negative gate pulse 8H is introduced. The output coupling capacitor 8H is connected at its free side to a signal pulse output terminal il i 8.

The values of resistors 805 and 813 are designated as R1 and Re, respectively. R1 is much greater than R2, for example, these may be 5,60() ohms and 300 ohms, respectively. The peak magnitude of the gate pulse Sli should be at least as great as that of the signal pulse 801, and is preferably slightly greater. if these conditions are provided, the gate pulse Ell is able to so bias the grounded side of the second rectifier Sil@ with respect to groundthat the signal pulse Esi cannot render junction ses negative with respect to said grounded side. Thus, if the gate pulse Si? and the signal pulse 853i occur simultaneously, the signal pulse 8M passes through capacitor S, resistor 805, and capacitor 8H to the output terminal 553i. In this condition, the gate is said to be open On the other hand, if the gate pulse BIT is absent, the signal pulse Bill is able to render junction 893 negative With respect to the grounded side of the second rectifier 889, and is therefore conducted to ground at S52 Via the second resistor 813. rlhe resistance of the rectifier dos when conductive is about ohms. Accordingly, the total resistance from the input terminal 8d2 to ground at 852 is 5,000 ohms, and junction 898 is 400 ohms from the grounded end of this resistance. Thus, there is in effect a voltage divider from the input terminal 8d2 to ground at 812 by Which the peak voltage of the signal pulse 8d! is reduced to about 47%@ of the original value. The resulting amount of signal pulse voltage that reaches the output terminal 818 is so small as to be inoperative upon the circiuts that follow, and, therefore, the gate is said to be closed in this condition.

IThe gate of Fig. 13 may be employed as a Weighting gate H, i2 or I3 in the system of Fig. l by bringing the binary number pulse 'i to the signal input terminal 8&2 and the gating pulse I8 to the gate pulse terminal Bi thereof. It may be employed as a shift gate d5, 31, 48 or 49 by applying the flip-nop output pulse S2 to the signal input terminal 35.32 and the shift readout pulse Q3 to the gate pulse terminal 646, or as a carry gate 35, 3'! or 3S by applying the count control pulse 4S to the gate pulse terminal SI5 'in place of the shift read-cut pulse Q3.

In the gate of Fig. 13, the Signal and gate 4pulses SGI and 8H, respectively, are both negative, Iand the output pulse is negative. In Fig. ifi, this gate is modified by inverting the connections to the tvvo rectiers E55 and BSS so that a positive input pulse 82| and a positive gate pulse 821 will produce a positive output pulse 82S. Otherwise, the gates of Figs. 13 and 14 are similar in construction and operation. Fig. 15 illu-strates a somewhat diierent gate wherein the -polarities of the signal and gate pulses are opposite.

In Fig. 15, a negative signal pulse 93! is brought to the input terminal 232 and coupled via a nrst coupling capacitor 833 to the junction 834 of a first resistor B35 and iirst rectiiier 83E. Rectifier 83S is connected to ground at 83T, and poled to clamp the input pulse 33! to be substantially purely negative, in the same manner as rectier 806 in Fig. 13. Resistor 835 is connect-ed at its other end to the junction 838 of a second rectifier 839 and a second resistor 84|. The second rectifier 839 is connected to ground at 842 and poled oppositely to the first rectifier 836. The other end of resistor 84| is connected to the junction 843 of a third rectifier 844 and one side of a gate pulse coupling capacitor 845. A positive gate pulse 846 is brought to the other side of the capacitor 845 via a gate pulse input terminal 841. The third rectifier 644 is connected to ground at 848 and poled to clamp the gate pulse 846 to be substantially purely positive. Junction 838 is connected via a signal output coupling capacitor 849 to a signal output terminal 850.

Resistors 835 and 84| are preferably of the same value, R3. In the absence of a signal pulse 83|, the gate pulse 846 passes through resistors 84| and 835 and rectifier 836 to ground at 831. The potential level of the gate pulse at junction 838 is sufiiciently high so that a positive signal pulse 85| appears at the output terminal 850. When the signal pulse 83| is pre-sent, it substantially cancels the positive gate pulse at junction 838. To this end, the magnitudes of the two input pulses 83| and 841 are preferably adjusted so that, when both are present, rectifier 839 becomes at least slightly conductive. The gate of Fig. is thus one in which, when a signal pulse 83| is present, there is no output pulse, but, when the signal pulse 83| is absent, there is an output pulse 85| of the opposite polarity. This gate has use in the present invention, as will be described later. Although many other forms of gates can be devised, and some others will be described later, an understanding of the foregoing gates will aid in the explanation of the operation of many parts of the systems described herein.

Referring now to Fig. 3, the diagram of this figure illustrates the operation of the fourcolumn regi-ster of Fig. 1 when binary number pulses are being brought thereto to create an indicator. During each step of this operation, the carry gates 36, 31 and 3'8 in Fig. 1 are all open, since the count control pulse 40 occurs simultaneously with each binary number pulse l1 or pulse space, while the shift gates 46 to 49, inclusive, are closed throughout the operation. A negative pulse 86 from the reset pulse generator is applied to the register, that is, to all the flip-flops in parallel, prior to commencing the operation. By so doing, triode 54 of each flipflop is rendenered nonconductive, thereby rendering triode 55 of each flip-flop conductive. Then, when the first pulse from a weighting gate is introduced into the register, it renders the triode 55 of the flip-flop to which it is applied noncond-uctive, so that a 1 stands in the flip-flop. Thus, if there is a pulse |1 in the rst binary number space, Vcolumn 1 flip-flop 2| stand-s at 1 when the pulse is applied through weighting gate #1. In the case where the binary number has a second pulse in the second binary number space, this second pulse is applied through weighting gate #2 to column 2 flip-flop 22, thereby causing flip-flop 22 also to stand at l. Consider now that the third binary number space of the input number is a zero. Then no pulse is applied to column 3 flip-flop 23 when weighting gate #3 is opened, and flip-flop 23 stands' at zero. If further the fourth binary number space contains a pulse this fourth lspace pulse is applied through weighting gate #l to column 1 flip-flop 2|, and initiates the following sequence of events. First, the fourth column number l 10 pulse renders triode 54 of column 1 flip-op 2| nonconductive and therefore renders triode 55 of the same flip-flop conductive. As a result, column 1 flip-flop 2| produces an output pulse 92 in its output line 3| and then stands at zero. The second event that takes place is that output pulse 92 from column 1 flip-flop 2| is carried via output line 3| to input line 2T of column 2 flipflop 22 Where it is effective in the same manner as a binary number pulse I1 from weighting gate #2. Therefore, column 2 flip-flop 22 is caused to stand at zero and to produce an output pulse 92 in its output line 32, which provides the pulse 92 to the input line 28 of column 3 flip-flop 23. It will be remembered that flip-flop 23 has, to this point, been standing at zero, and now is caused to stand at 1 by the output pulse 92 from the column 2 flipop 22. Thus, the register has performed the addition of binary number 1 to binary number 0 1 1 and now stands at the sum of those numbers, which is 1 0 0 in the binary system.

1n the same fashion, the register illustrated in Fig. 3 continues to add digits represented by pulses applied to the various flip-flops in columns 2 and 3. However, the register shown in Fig. 3 differs from an ordinary adding device in that it is limited to four columns. Thus, when this register arrives at binary I5, which is expressed 1 1 1 1 in the binary system, the addition of a single pulse in column namely, the addition of binary 1, causes the register to stand at 0 0 O 0. As is known, the binary representation of 16 is 1 0 0 0 0, but the register shown in Fig. 3 is lacking a fth column, and, therefore, represents binary 16 by 0 0 0 0. Thus, binary 17 is represented by 0 0 0 1, which is the same as the binary representation of 1. It is apparent, therefore, that the register shown in Fig. 3 counts up to 15 and starts over again at zero with 16, thereafter counting 17 to 31 in the same manner as 1 to l5, respectively, and starting over again with 32. This process is repeated at 48, 64, and all integral multiples of 16. The register of Fig. 3 is accordingly called a modulo 16 counter. It has the property that regardless of the magnitude of a binary number that is provided from the binary number input 10, after the entire binary number has been applied to it as shown in Fig. 1, it stands at a particular four-column binary number which is arrived at by a process in which the columns of the original binary number being treated are weighted, from right to left, in the fashion 1 2 4 l 2 4 1 2 4, and then the weighted sum of those columns wherein there is a l is taken in the fashion modulo 16 as set forth above; that is, the first column binary digit commencing at the right-hand side of the Abinary number input is applied to column the digit of the secon-d column to the left to column 2, the digit of the third column to the left to column 3, the digit of the fourth column to the left to column etc. As will be recognized, a digit in column 3 represents binary number 4, a digit in column 2 represents binary number 2, and a digit in column represents binary number 1. Hence, the various columns of the original binary number input are considered to be weighted in the manner set forth, and, therefore, the gates |2 and I3 are called weighting gates.

Fig. 4 illustrates the register of Fig. 1 as arranged to read out the information stored therein. The four-column binary number indicator which is generated by the register may be read out of the register at any desired pulse repetition frequency which is controlled by the frequency with which the reset pulse generator produces reset pulses 86. The shift read-out control pulse generator produces a shift read-cut pulse S3 substantially simultaneously with the production of each reset pulse 86, so that the shift gates 4t to 49, inclusive, are all opened each time a reset pulse 86 is produced. Consider, for example, that the four-column binary number 1 1 G 1 stands in the register. Now apply a reset pulse 8| from the reset pulse generator to the register. This pulse is applied to the first triode 5ft of each flipflop, which triode is conductive in each flip-flop which stands at l and nonconductive in each fiip flop which stands at zero. Being negative, the

pulse 86 renders triode 54 nonconductive in each nip-flop that stands at i, namely, the column 4, 3 and flip-flops 24, 23 and 2|, respectively, causing all the fiip-ops to stand at zero. In the case of the column 4, 3 and fiip-ops 24, 23 and 2|, respectively, this change causes the second triode 55 to become conductive, and, therefore, each of flip-flops 24, 23 and 2| produces an output pulse 32 in output lines 34, 33 and 3|, respectively. The output pulse 92 from line 3| is available via the serial read-out terminal (Fig. l) to a succeeding circuit, and may be said to have been read out. Thus, the serial read-out terminal 5i) may be connected to the memory of a complete computer system (not shown), Where its output can be stored together with the original binary number, in the manner illustrate-d in Fig. 5, for example, and through the memory to the Word input line of Fig. 6, as will presently appear. After suitable delay furnished by the delay lines 44 and :i3 which permits the output pulse 92 from the first column flip-nop 2| to be removed, the reset and shift read-out pulses 86 and 93, respectively, to terminate, and the shift gates 43 to 4.2i, inclusive, to become closed, the output pulses 92 in lines 34 and 33, respectively, are provided to the control grids of the secon-d triodes 55 of the column 3 and 2 flip-flops 23 and 22, respectively. As a result, the second triode of each of columns 2 and 3 isv again rendered nonconductive, so that a 1 stands in each of columns 2 and 3. Since the column 2 flip-flop 2v2 produces no output pulse 92 the column flip-flop 2| stands at zero. Thus, in response to the first reset pulse 88 from the reset pulse generator 20, the binary number 1 1 0 1 is shifted one column to the right in the register which now stands at 0 1 1 O, and the extreme right-hand -digit of the original numn ber has been read out. Because of this shifting action, the register employed as in Fig. 4 is termed a shift register.

Similar considerations to the foregoing make apparent the fact that each reset pulse 86 causes the number standing in the shift register to shift one column to the right and simultaneously causes the extreme right-hand digit to be read out. Thus, the repetition rate with which a number standing in the register is read out is determined by the repetition rate of the reset pulses 86. The number 1 1 0 1 can, therefore, be read out as 1 1 0 1 at any pulse repetition frequency desired.

If desired, a binary number can be serially read into the shift register of Fig. 4 by applying the number at an input line 8| brought into the first side of the column 4 flip-flop 2li. This input line is connected to the fiip-flop as line 3|! is connected to flip-flop 2| in Fig. 1, for example. The process of reading in is to apply the rstcolumn binary number information via line 8| to act upon iiip-fiop 24, and then to shift the information to the right in the register with a reset pulse This process is repeated until the binary number has been read into the register. Obviously in this arrangement, a shift register constructed as shown in Fig. 4 may have as many columns as are necessary to accept the incoming binary number. A shift register employed in this manner has utility in a system to be described below. The reading out of binary-form information so store-d in the shift register is exactly the same as described above.

The function of the shift gates 45, 4l', 48 and i9 and the carry gates 35.5, 3'! and 38 now becomes app-arent. Referring again to Fig. 1, it will be noted that the output lines 3|, 32 and 33 are each connected in parallel to an input to both adjacent ip-iiops. The carry gates 36, 3l and 38 are opened when it is desired to carry the output from a flip-nop of one column to the next higher column nip-nop, that is, when a binary number is being Weighted and information is being put into the register to generate an indicator. The shift lgates 35, iii, 48 and 49 are opened When a number is being read out of the register. Therefore, the count control pulse generator 39 provides its pulse 4a to open the carry gates 36, ii'i and 38 in synchronism with the pulses I1 of the binary number which is being weighted, and the shift. read-out control pulse generator 5| provides its pulses 93 to open the shift gates 46, 41, El and 49 simultaneously with the reset pulses st of the reset pulse generator 26. In this manner the two functions of the register of Fig. l are maintained separate and distinct.

When a binary number is treated in the foregoing apparatus, the four-column binary number that is generated in the register may be termed Aan indicator for the reason that it has a characteristic value which depends upon the original binary number. Since the indicator is generated by a method of weighted count, that is, a method wherein each column of the original binary number is weighted in accordance with a prescribed scheme prior to being coun-ted, the indicator may also be termed the weighted count of the binary number.

For the purpose of monitoring or supervising the identity of a binary .number in any system, the Weighted count or indicator is preferably generated immediately upon the creation of the binary number itself, and thereafter carried with it throughout the complete computer system. For example, a binarynumber and its count are illustrated in Fig. 5, where a fifteencolumn binary number and its Weighted count are shown. On line A A of Fig. 5 there is illustrated, starting at the left-hand end, a fifteencolumn binary number comprising pulses Il, each of which represents the digit l, and empty pulse spaces e8, each of which represents a zero.v The fifteen-column binary number shown on line A-A thus represents the binary number which is shown on line B-B Following the number to the right, there is a single space 95 which is reserved for the algebraic sign of the number, as is desirable when the number represents a mathematical quantity. In the present example, the absence of a pulse in the space 9B is representative of a sign, and the presence of a pulse in that space is representative of a sign. In the example shown in Fig. 5, the

13 sign oi the fifteen-column binary number is (+3 as shown on line B-B, since there is no pulse present in space 96 in line A-A. Further to the right beyond the sign space 96 are the pulses of the weighted count, which constitute a fourcolumn binary number. The weighted count in the present example is the binary number 0 1 0 where the digit 1 is represented by a single pulse 9'1 in the second column, the rest of the pulse columns being blank. The weighted count shown in Fig. was generated by weighting columns of the binary number, starting at the right-hand end, in accordance with the arrangement set forth above. However, column 96, reserved for the algebraic sign, is, in this example, included with the number so that actually 16 columns were weighted. The reason for this is that for mathematical purposes it is deisrable to know not only when a pulse has been lost or gained in the number itself, but whether or not the algebraic sign is correct. Weighting the binary number and its sign in Fig. 5 in accordance with the weights etc., from right to left, would yield a weight of 17, which is binary number 0 O 0 1. However, since the number zero is the same in both the binary and decimal systems, that is, the same for base 2 and base I0, binary number 1 is added to the weighted count 17 in order that the binary number and its count may never both simultaneously be Zero. Thus, the weighted count shown in Fig. 5 is 18, or binary number 0 0 1 0, instead of 17, as would be expected. Binary number l is added in Fig. 1 by means of the add 1 pulse generator 25 which is operated to add 1 pulse through the column I iiip-iiop 2| at the end of the generation of a weighted count or indicator. In this manner, if a pulse is lost or gained in any binary number or its weighted count, the fact can be detected by apparatus to be described below.

As has been set forth, it is preferable, once a binary number and its sign appear in a system, immediately to generate an indicator which is here a weighted count in the form of a fourcolumn binary number, and to carry the indicator at all times with the original binary number and its sign. The arrangement shown in Fig. 5 which includes the number, its sign, and its weighted count in one group of pulses, is termedfone word. One word for a fifteencolumn binary number, its sign, and a fourcolumn indicator includes 20 columns. In a conservative system, each pulse space may be ten microseconds wide and each pulse, when it occurs, one microsecond wide within that space. This provides ample separation between pulses and ample opportunity to detect the absence of a pulse indicating a zero in a particular column. A twenty-column word, as shown in Fig. 5, is, with this column interval, 200 microseconds long, or one five-thousandths of a second. With such rapidity of operation, it should be obvious that a means of checking the identity of a number and its sign each time they are handled is of extreme value, if the speed with which they can be handled is to be enjoyed. It is possible to employ the present checking system with its characteristic indicators in various systems, including all forms of pulse telemetering and pulsetype calculating systems.

Referring now to Fig. 6, the apparatus there shown supervises the identity of a binary number which has been converted to a word of the kind shown in Fig. 5. In systems which employ binary notation, particularly, for example, calculating machines, the entire word may be stored for a period of time in a memory system (not shown). Examples of such memory systems are mercury delay lines and recirculating circuits for short-term storage, or magnetic tapes which are moved mechanically for long-term storage. Whenever it is desired to inject a particular bit of information into a calculation or a presentation of information, the binary number or binary pulse series which represents the information is extracted from the memory. The apparatus shown in Fig. 6 accepts the word, which includes the binary number information, separates the number and its sign from the indicator, stores the original indicator in a register similar to that shown in Fig. l, generates from the number and its sign a new indicator in a weighted count indicator generator similar to that shown in Fig. l, and then compares the original indicator with the newly generated indicator to determine whether or not the binary number that has been extracted from the memory is the same as the binary number which was furnished to the memory.

The apparatus of Fig. 6 includes a gate |0| into which is introduced the word which is being transferred from memory. A synchronizing or clock pulse |02, which is a pulse furnished by any suitable central control pulse generator for the purpose of initiating the operation of the apparatus, is applied at an input terminal |03, which is connected in parallel to a delay line |04 and a gate control pulse generator I 05. The gate control pulse generator has two output lines |06 and |07 in the rst of which it provides a control pulse |08 and in the second of which it provides ya control pulse |09, when it is triggered by the clock pulse |02. The gate control pulse generator |05 will be of any suitable form, for example, a multivibrator, which produces the pulses |08 and |09 with a separation of substantially four columns of the Word, as shown on line C--C in Fig, 5. The clock pulse is furnished also to the word input gate IOI through the delay line |04 and opens the grate to call the Word out of the memory at about the same time that the first gate control pulse |08 is generated by the gate control pulse generator |05. The control pulse |08 goes to a count gate III, via line |00, for the purpose of opening that gate. The indicator, which is the four-column binary number having the pulses of the weighted count, yappears first; that is, the word appears to be coming out of the memory with the extreme right-hand column in Fig. 5 appearing rst.

The rst four columns of the word occur when the count gate is open and are presented to a four-column register ||0 like that of Fig. 4, comprising nip-flops |2| to |24, inclusive, and delay lines |31 to |39, inclusive, corresponding to flip-flops 2| to 24, respectively, and delay lines 42 to 44, respectively, in Fig. 4, va an input line I|3 to the column 4 fiip-op |24 which corresponds to the input line 8| of Fig. 4. All four flip-hops in the shift register |I0 are previously cleared to stand at zero by 'a reset pulse I 29 from a reset pulse generator |20, similar to the reset pulse generator 20 of Fig. 1. The reset pulse generator |20 is set into operation by the clock pulse |02 via line 2 and generates suiiicient reset pulses |29 to clear the shift register and read in the weighted count of the word. Since there is no need for the separation of two func tions as in Fig. 1, shift register il!) is not provided with shift gates. There now stands in the shift register H6 the original weighted count 0 l O of the word (Fig. 5) being transferred.

Between the fourth and iifth pulse spaces of the word being transferred, the gate control pulse generator |65 provides the second control pulse ica in line |01 which opens a number gate |26, which gate remains open for the rest of the word, namely, for 16 pulse spaces, or, in the particular example set forth above, for 160 microseconds. Accordingly, the sign and the entire iifteencoiumn binary number' are furnished to a binary number input |21 similar to the binary number input le of Fig. i. This may be any suitable arrangement for providing the binary number pulses with proper polarity or shape and, if not needed, may be omitted. In any event, the numbei' and its vsign are provided to a weighted count or indicator generator 28 which incorporates all the features of the circuit sh-own in Fig. l, including a similar four-column register wherein a new weighted count or indicator is generated and stored.' If the binary number and its sign have not been altered in the handling or in the memory, the weighted count which is generated in the generator |28 and the original weighted count which is stored in the shift register IIB are identical.

The original count and the newly generated count are read out simultaneously through lines 13| and |32, respectively, into a coincidence circuit |33 under the control of the reset pulse generator |20. The reset pulse generator is again actuated by any suitable means (not shown), and provides the reset pulses |23, which are furnished simultaneously to the shift register I6 and the register f the new indicator generator |28, containing the original and newly generated weighted counts, respectively. in the same manner as described above, the pulses of the two weighted counts appear in the serial read-out lines |B| and |32, respectively. Corresponding pulses of each weighted count appear simultaneously at the coincidence circuit |33, which has the function of detecting when the simultaneously presented pairs of vpulses or pulse spaces are alike and when they are diierent from each other. tical, that is, should their corresponding pairs of pulses or pulse spaces be the same, the system which the invention `is supervising is permitted to proceed. On the other hand, should the pulses or pulse spaces of any corresponding pair in the two weighted counts diner, that is, if one pulse space has no pulse in one weighted count and the corresponding pulse space has a pulse in the other weighted count, an error signal will appear in output line |35, which signal may be employed to stop the supervised system, give an alarm, or indicate where in the supervised system the fault lies, as desired.

Fig. 7 illustrates a suitable coincidence circuit |33 for useV in the apparatus of Fig. 6. One of the input lines, for example |62, is brought to a cathode follower llil which accepts a weighted count negative pulse e?! via a capacitor |42 at its input and provides `a pulse ist of the same polarit-yacross the output resistor M3 thereof. The cathode follower is provided for isolating purposes. only,y and being a well-known device is not further described. The negative pulse |46 is carriedA via a .coupling capacitor |44 to a gate 6 of the .kind .shown in Fig. 15, including in Should the tw-o weighted counts be idenseries a resistor |45, and a rectifying device |46 poled to conduct negative pulses to ground at |41. The rectiiying device |46 and other similar rectifying devices in this circuit may again be any suitable unidirectional conductor, for example, a diode electron tube device or a crystal, and these devices wiil be hereafter referred to by the term rectiiien A positive pulse |56, which will be termed a clock pulse i introduced at a first clock pulse input terminal which is connected via a coupling capacitor |52, a resistor |53, resistor |45, and a rectifier |54 in series to ground at |55. Rectifier |54 is poled to maintain the negative pulse i4@ purely negative with relation to ground. At the junction point |56 between resistors and |53, the negative pulse |46 and the positive clock puise |50 are in voltage opposition and tend to cancel each other when they occur simultaneously. The resistors |45 and |53 are preferably oi the saine value, in the neighborhood of 5Go ohms. A rectiiei- |62 is connected from the junction of coupling capacitor |52 and resistor |53 to ground at |58, and poled to maintain the positive pulse |56 purely positive with relation to ground.

The junction point |56 is connected via a coupling .capacitor |66 to the control grid i6! of an electronic relay i62 which includes an electron tube 63. The cathode |64 or this electron tube is connected to ground at it and through a biasing resistor itt and a voltage `dropping resistor iti' in series to a source of potential B. which is negative with respect to ground. The control grid is connected via a current limiting resistor i68 to the junction oi the biasing resistor |66 and the voltage dropping resistor |61, and is normally maintained at a potential which is negative with respect to that of the cathode |64 by an amount equal to the voltage drop in the biasing resistor i66. The anode H6 of the electron tube |63 is provided with voltage which is positive with respect to ground from a source 'B-lthereof via a load resistor 'il and the primary |12 of a transformer i'i'ii. The screen grid |14 of the tube |63 is provided with suitable potential from B+ via resistor lli and an additional dropping resistor liti in series, and is coupled to ground at |65 by a .capacitor H6 which acts as a bypass capacitor in the usual manner. An additional bypass capacitor H3 is connected from Athe junction of resistors |l| and V to ground at '19. .A rectifier ist is connected across the primary winding |12, poled to conduct positive pulses from the anode side to the resistor side thereof. The bias on the control grid or the electron tube |66 is such that the tube is normally cut off or substantially so, so that a positive pulse applied to the control grid i6! causes an increase in current through the tube, and, therefore, a corresponding current surge in the primary winding |12. A negative pulse il is produced at the anode |10, since the lower .end of the primary winding becomes negative with respect to the upper end thereof. Any positive pulse, that is, a pulse of the opposite polarity, which tends to develop in the primary winding |"2 when the electron tube |63 is again returned toward cutoff, is substantially shortcircuited by the shunt connected rectifier |80.

It will be recalled that the weighted count consists of a series of four pulse spaces, each of which may be blank or may contain a negative pulse 91. Clock pulses |56 are provided to the coincidence circuit by any suitable pulse generator with regularity, one for each pulse space of the weightedv count and simultaneously` with the pulses 91 should the latter exist. Thus, if a pulse 91 exists in the weighted count which is introduced on input line |32, it substantially cancels out the concomitant clock pulse 50, and there is no negative pulse |8| provided at the anode |10 of the relay |62. On the other hand, should a pulse space of the weighted count be vacant, the clock pulse |50 which is furnished during that pulse space is not cancelled, and is provided to the control grid |6| of the relay tube |63, thereby causing the negative pulse |8| to occur at the anode |10.

The secondary winding of the transformer |13 is made up of two parts |83 and |04 serially joined together and connected at their junction point to ground at |85. Accordingly, in response to the surge of current which produced pulse |8| in the primary winding |12, there appears at the free endlof secondary section |83 a pulse |06 which is negative with respect to ground, and at the free end of secondary section |04 a pulse |61 which is positive with respect to ground. A path for the positive secondary pulse |81 to ground is pro vided via a coupling capacitor |9|, a resistor |92, a rectifier |93 and a second resistor |94 in series to ground at |95. The rectifier |93 is suitably poled to pass the positive secondary pulse |81 to ground in this circuit. An additional rectifier |96 is connected from the junctionof the coupling capacitor |9| and resistor |92 to ground at |91 and suitably poled to remove from this circuit any -voltage which'may appear which is negative with respect tov ground. As a result, the positive pulse '|81' which appears in the series circuit of resistor |92, rectifier |93 and resistor |94 is wholly positive with respect to ground. A path for the negative secondary pulse |06 is provided to ground at 20| via a resistor 202. A rectifier V203 is connected at one vside to the junction of resistor 202 and secondary section |03, and to the other side to a point 204 by Way of which a connection is made to further circuit elements to be described below. Rectifier 203 is poled to conduct the negative pulse |06 to point 204.

The other Weighted count input line |3| is connected to a second electronic relay 205 which includes an electron tube 206. The negative pulses 91 of the weighted count which is brought in via line |3| are applied to the control grid 201 of the electron tube 206 via a coupling capacitor 208. The anode 209 of the electron tube 206 is provided with anode potential from a'source B+ thereof via a resistor 2| and the primary Winding 2|2 of a transformer 2|3 in series. A rectiafler 2|4 is connected in shunt with the primary winding 2|2, being poled to conduct a negative pulse from the anode end to the resistor end thereof. The cathode 2 |5 of the tube 206 is connected directly to ground at 2 I6 and to a source, B-, of potential which is negative with respect to ground via a biasing resistor 2 1 and a voltage dropping resistor 2|0 in series. The control grid 201 is connected to the junction of these two resistors via a current-limiting resistor 2| 9. lThe screen grid 22| is provided with suitable potential from the B+ source via the yanode resistor 2| and an additional dropping resistor 222 in series, and is bypassed to ground at 2|6 via a bypass capacitor 223. =An additional bypass capacitor 224 is connected from the junction of the resistors12|| and 222 to ground at 225. The circuitof relay 205 will be recognized as similar in manyI respects to the circuit of relay |62. However,''the bias resistor 2 |1 of relay 205 is substantiallygf'smaller than the bias resistor |66 of relay |62 with the result that the electron tube 206 is normally in a conductive state. Thus, when a negative pulse 91 is applied to the control grid 201, the tube 206 becomes less conductive and a positive pulse 226 appears at the anode 209, since the lower or anode end of the primary Wind'uig 2|2 becomes positive with respect to the upper or B+ end thereof.

The secondary Winding of transformer 2 3 consists of two sections 228 and 229 serially connected with their junction point grounded at 230. The secondary sections are so poled that a pulse 23| which is negative With respect to ground appears at the free end of section 228, and a' pulse 232 which is positive with respect to ground appears at the free end of section 229'. The free end of section 229 is connected to the junction point 233 of rectifier |93 and resistor |94 of the circuit of the positive pulse |81 which is provided by relay |62.v By Way of this connection, the positive pulse 232 is able to bias the rectifier |93 to a nonconductive state as far as positive pulse |81 is concerned. As a consequence, when the positive pulse 232 exists simultaneously with 1 a positive pulse |81, positive pulse |81 proceeds -along line 235 instead of being conducted to ground at |95.

The negative pulse 23| is connected to point 204 via a rectilier` 236 Whichis. suitably poled to conduct negative pulses to said point. It will be recalled that negative pulse |86 is also provided .to point 204 via rectifying device 203. g The clock pulse |50 is provided also to a second clock pulse input terminal 238, which is connected by Way of a coupling capacitor 24|, resistors 242 and 243, and a rectier 244,.in series, to ground at 245. The junction of resistor 243 and rectiiier 244 is directly connected tor point 204, and this point is connected via a resistor 246 to ground at 241. The rectifier 244 is suitably poled to conduct positive pulses like Athe clock pulse |50 to ground at 245. Another recti- -iier 248 is connected from the junction 250 of resistors 242 and 243 to ground at 25|, and is suitably poled to conduct negative pulses to ground. Still another rectifier 252 is connected from the junction of capacitor 24| and resistor 242 to ground at 253 and is suitably poled to conduct negative pulses to ground. This arrangement will be recognized as similar in many respects to gate ||6, with inputs at point 204 and terminal 238, and an output at junction 250. A negative pulse |86 or 23| flows through resistor 243 to ground at 25| via rectifier 248, while the clock pulse |50 iiows through resistors 242 and 243 to ground at 245 via rectifier 244. Thus, at junction point 250 either one of negative pulses |86 or 23| can be in opposition to the positive clock pulse |53. In this respect, junction point 250 and junction point |56 are similar.

Output line 235 is connected via a coupling capacitor 255 to the liirst control grid 256 of a double triode type electron tube 251. A resistor 258 is connected between the first control grid and ground at 259. Junction point 250 is connected via a Vcoupling capacitor 260 to the second control grid 26| of the double triode 251, and a resistor 262 is connected from said second control grid to ground at 263. The two anodes 264 and 265 of the tube are connected together and via an anode resistor 266 to a source, B+of anode potential and bypassed to ground at 29| via a bypass capacitor 292. The two cathodes 261 and 268 of the tube 251 are connected together and via a cathode resistor 269 to ground at 210. An additional electron tube 21| including an anode 212, control grid 213 and cathode 2154* `has its' control grid 213' connected via a cou'- Lpling' capacitor 215' to the junction of the cathode resistor 269 and the cathodes of the double triod'e tube 251. .Anode potential is supplied to the tube 21 I' from the source B+ of anode volt'- age via. an -anode circuit resistor 21'6'. The cathode 214i of the. tube 21| isI grounded at 211 and Vconnected via a biasing resistor 218 and current -limiting` resistor 219 to a source, B'-,l ofv potential Vwhich is negative with respect to ground. The grid' 213 is' connected to the junction of resistors 218 and '219 via a current-limiting resistor 280. The output. signal connection |35 is made from the anode 212 of; tube 21| via an output coupling ,capacitor 28|.

The double triode tube 251 is normally conductive andl self-biasing at the cathode by virtue of the cathode resistor 269 which may be, approximatelyI 3,000 ohms. When. the positive pulse |81 proceeds along line 235 to. the rst control grid 2.'||5',I it. renders one triode section of the double triode tube. 251" more conductive, so that a corresponding positive pulse 283 appearsy in the cathode resistor 269. When the clock pulse |50 which is introduced at clock pulse input terminal 238' is not opposed by a negative pulse |86 or 23|, itis impressed upon the second control grid 26| and renders the other tricde section conductive, causing the positive output pulse 283 to appear. The output tube 2`1| is normally `cut oftby the bias voltage in resistor 218, and is rendered conductive by the positive output pulse 283. This results in the production of a negative output pulse 284 in the output line |35, which is the error signal.

The operation of the circuit of Fig. should now be readily understood. ThereA are four con.- ditionsl which the circuit is called upon to determine. These are. as follows: I.. The vcondition in. which a vacant pulse space, representativeA of a Zero, is presented in line |3|, and a similar vacant pulse space is presented in line |32. In this condition, the clock pulse |56 introduced at terminal |5| is not opposed at point |56, and the'negative and positive pulses' |86 and |81 are generated, while, at the same time, the negative and positive pulses 23| and 232 are not generated. Consequently, positive Vpulse 232 being` absent, positive pulse |31 proceeds to ground at |35. Negative pulse |86, however, opposes positive clock pulse |53 at point 2150. Therefore, neither of the control grids 256 or 26| is altered in potential and no error signalr pulse 234 results. lis the desired operation, for the two input lines have received similar information.

2. The condition in which .a vacant pulse space is presented to input line |31 and a negative pulse 91 is presented to input line |32. In this condition, the negative and positive pulses |86 and |81, respectively, are not generated, and the negative. and positive pulses 23| and 232., respectively, are not generated. As a result, clock pulse |58 is'` unopposed at point 2.50, and proceeds .to the second control grid 26| of the double triode tube 2.51, providing an error signal pulse 284. This i-s the desired operation of the circuit, for now there is lack of concidence between the information provided in the two input lines |3| and |32. i

3. A situation in which a negative pulse 91 is provided in line |3| and a vacant pulse space is presented in line |32'. In this situation, negative and positive pulses |86 and |81 are generated and negative and positive pulses 213| and 232 are generated. Positive pulse 232 biases rectier |93 to a non-conductivev state with respect to posi-"- tive pulse |81, and positive pulsev |81 proceeds via line 235 and' capacitor 255 to therst control grid 256 of' the double triode 251, causing the generation of an error signal pulse 2841 to warn ofthe lack of coincidence.

4. Thev situation in which a negative pulse 91 is provided at each o-f the input lines |3|. and |32. In this situation, the negative and positive pulses |86 and |81 are not generated, while the negative and positive pulses 23|' and 232 are generated. Negative pulse 23| opposes positive clock pulse at point 250, as a result of which no alarm pulse is generated This is the desired operation, for nowy there is coincidence. of the-'information at the two input lines |3| and |32.

It is convenient now to. review the invention as far as it has been described. The fundamental basis of binary Vnotation is that the successive digits: of a binary' quantityI .may besaid to be vvralued or weighted from. right tov left with the value 2', where 'n the column number, starting at,y the right-hand end of the quantityn The conventional orv decimal system valuey 'of the binary quantity isy then the sum of the weights of' all of those columns in which a 1 appears. In accordance with the present invention,y a different value is obtained lby weightingv the columns in a. different, arbitrarily chosen. manner. Any weighting scheme different from the scheme that yields the conventional value may be used; in the example described herein, the apparatus was designed to employ the Weights 21, 4, l, 2, 4, 2, 4, etc. for the successive columns from right to left. A new number is then found which is the sum. of the new weights of all columns in which the digit 1 occurs. This new number, or rather the lowest order four digits oi it, is called the weighted count ot the original number and is carried with it as an indicator at all times. The modulo 16 counter described in Figs. 1,-4, and more particularly in Fig. 3, provides the weighted count. To prevent the number and its count from ever being both zero simultaneously, the digit 1 is added to the. weighted count in the first column. Thus, a complete failurey in transmission of a number and its count will. be detected. In the case of a computing, machine, each number stored in the memory has its weighted count. stored with it (Fig. 5'), and the. complete loss of both in storage is similarly detected. A number is checked at any time., particularly during a vtransfer from one place Itol another by iormulating a new weighted count and Ychecking this for identity with the weighted count carried with the number (Figs. Gand 7,).

The monitoring system of the invention is not limited to the weighting scheme. 12, 4, l., 2, 4, etc.; in fact, any arbitrary vweights couldl be. assigned to the columns. For example, the columns of the binary quantity maybe weighted 1, 1, l, l, etc. Here the summation consists merely of adding' up the number of ls which appear in the quantity. This scheme of weighting and counting does not consti-tute as good a check as the 1, 2, 4 scheme described above since a loss of a 1 in a given column can be compensated for by the gain of a 1 in any other column which originally held a zero, whereas, in the l, 2, 4 scheme, a very odd combination of circumstances is needed to render the number incorrect and at the same time render a newly generated weighted count correct. For example, suppose'the binary quantity were to lose four ls in columns 3,' 6, 9 

